add in RDF dataset definitions from SPARQL query

spec/index.html

@@ -1498,6 +1498,60 @@ <h2>RDF Datasets</h2>
     between datasets would require RDF graph entailments between the graphs with the same name
     (adding in empty graphs as required).</p>
 
+  <table>
+    <caption>Definition of an RDF dataset</caption>
+    <tr>
+       <td class="semantictable">
+       <p>An <dfn data-lt="RDF dataset">RDF dataset</dfn> I is a set:</p>
+              { G, (&lt;u<sub>1</sub>&gt;, G<sub>1</sub>), (&lt;u<sub>2</sub>&gt;, G<sub>2</sub>), . .
+              . (&lt;u<sub>n</sub>&gt;, G<sub>n</sub>) }<br>
+              where n&ge;0 and G and each G<sub>i</sub> are graphs, and each &lt;u<sub>i</sub>&gt; is an IRI. Each
+              &lt;u<sub>i</sub>&gt; is distinct.</p>
+            <p>G is called the default graph. (&lt;u<sub>i</sub>&gt;, G<sub>i</sub>) are called named
+              graphs.</p>
+        </td>
+    </tr>
+  </table>
+  <table>
+    <caption>Definition of active graph in an RDF dataset</caption>
+    <tr>
+       <td class="semantictable">
+            <p>The <dfn data-lt="active graph">active graph</dfn> in an RDF dataset is the graph from the dataset used for basic graph pattern
+              matching.</p>
+       </td>
+    </tr>
+  </table>
+
+  <table>
+    <caption>Definition of RDF dataset merge</caption>
+    <tr>
+       <td class="semantictable">
+            <p>Let DS1 = { G1, (&lt;u1<sub>1</sub>&gt;, G1<sub>1</sub>), (&lt;u1<sub>2</sub>&gt;,
+              G1<sub>2</sub>), . . . (&lt;u1<sub>n</sub>&gt;, G1<sub>n</sub>) },<br>
+              and DS2 = { G2, (&lt;u2<sub>1</sub>&gt;, G2<sub>1</sub>), (&lt;u2<sub>2</sub>&gt;,
+              G2<sub>2</sub>), . . . (&lt;u2<sub>m</sub>&gt;, G2<sub>m</sub>) }</p>
+            <p>The <dfn data-lt="RDF dataset">RDF dataset merge</dfn> of DS1 and DS2 is:<br>
+              DS={ G, (&lt;u<sub>1</sub>&gt;, G<sub>1</sub>), (&lt;u<sub>2</sub>&gt;, G<sub>2</sub>), .
+              . . (&lt;u<sub>k</sub>&gt;, G<sub>k</sub>) }<br>
+              where:</p>
+            <p>Write N1 for { &lt;u1<sub>j</sub>&gt; j = 1 to n }<br>
+              Write N2 for { &lt;u2<sub>j</sub>&gt; j = 1 to m }<br></p>
+            <ul>
+              <li>G is the <a data-cite="RDF12-SEMANTICS#dfn-merge">merge</a> of G1 and G2
+              </li>
+              <li>(&lt;u<sub>i</sub>&gt;, G<sub>i</sub>) where &lt;u<sub>i</sub>&gt; is in N1 but not
+                in N2</li>
+              <li>(&lt;u<sub>i</sub>&gt;, G<sub>i</sub>) where &lt;u<sub>i</sub>&gt; is in N2 but not
+                in N1</li>
+              <li>(&lt;u<sub>i</sub>&gt;, G<sub>i</sub>) where &lt;u<sub>i</sub>&gt; is equal to
+                &lt;u<sub>j</sub>&gt; in N1 and equal to &lt;u<sub>k</sub>&gt; in N2 and G<sub>i</sub>
+                is the <a data-cite="RDF12-SEMANTICS#dfn-merge">merge</a> of G1<sub>j</sub> and G2<sub>k</sub>
+              </li>
+            </ul>
+        </td>
+    </tr>
+  </table>
+
 </section>
 
 <h2 id="appendices">Appendices</h2>